Patent RU-2537472-C1 (RU)
Inventor: KASATKIN BORIS ANATOL EVICH
IPC: G01S15/00
Filed: 2013-06-26
Granted: 2015-01-10
Abstract: FIELD: physics, acoustics. 
     SUBSTANCE: invention relates to hydroacoustics and can be used to detect a submerged moving sound source, measure coordinates of a sound source in a shallow sea in passive mode using acoustic receivers mounted at the sea bed, coordinates and the angular position of which are considered known. The hydroacoustic measurement system comprises N acoustic composite receivers, each consisting of a hydrophone, a three-component vector receiver and amplifiers connected thereto, a telemetric unit which includes voltage dividers, an analogue-to-digital conversion circuit, a single electronic multiplexing circuit, a modulator and an optical emitter connected by an optical link to an optical receiver, an information collection, processing and transmission system which comprises an information collection, processing and transmission unit and a device for accessing digital data networks. The acoustic composite receivers form two bottom vertically oriented equidistant antennae, in each of which the number of elements is equal to N/2, and local coordinate systems of all acoustic composite receivers are superimposed. The distance between vertical antennae 1>λ n , where λ n  is the wavelength at the lower frequency of the operating noise emission range of the sound source, the distance between the acoustic composite receivers is equal to a given error in determining the vertical coordinate (horizon) of the sound source Δz, and the number of receivers in each antenna N/2=h 12 /Δz, h 12 =z 1 -z 2 , where z 1 , z 2  are the lower and upper horizons of the probable location of the sound source, which form a detection corridor. Also, an information collection, processing and display system further includes an N-channel unit for calculating the vertical component of the intensity vector, a unit for determining the maximum of the vertical component of the intensity vector, an N-channel unit for calculating horizontal components of the intensity vector, an N-channel unit for calculating azimuth angles φ 1n , φ 2n , a unit for calculating averaged azimuth angles, a unit for calculating horizontal coordinates of the sound source. Information from the output of the unit for calculating horizontal coordinates of the sound source and the unit for determining the maximum of the vertical component of the intensity vector is transmitted to the first and second inputs of the device for accessing digital data networks. To increase the detection range of a moving sound source and maintain acoustic contact with said source, the information collection, processing and display system further includes an N/2 channel signal cross-spectrum computer for pairs of acoustic composite receivers lying on the same horizon and belonging to two bottom vertically oriented equidistant antennae, an N/2 channel cross-correlation function computer, an adder, a unit for measuring the maximum of the cross-correlation function, a unit for normalising the cross-correlation function, a unit for calculating the width of the main lobe of the normalised cross-correlation function, a computer of the ratio of the previous measurement to the last measurement at each step, a comparator, a unit for setting calculated values of the ratio of the previous measurement to the last measurement, a unit for making a decision on detection of sound sources and the number thereof. 
     EFFECT: reduced measurement error and longer range when the measurement system is operating on a shallow sea. 
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